ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 212 insertions, 0 deletions

diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
new file mode 100644
index 000000000..8eeb447ac
--- /dev/null
+++ b/drivers/nfc/virtual_ncidev.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtual NCI device simulation driver
+ *
+ * Copyright (C) 2020 Samsung Electronics
+ * Bongsu Jeon <bongsu.jeon@samsung.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/wait.h>
+#include <net/nfc/nci_core.h>
+
+#define IOCTL_GET_NCIDEV_IDX    0
+#define VIRTUAL_NFC_PROTOCOLS	(NFC_PROTO_JEWEL_MASK | \
+				 NFC_PROTO_MIFARE_MASK | \
+				 NFC_PROTO_FELICA_MASK | \
+				 NFC_PROTO_ISO14443_MASK | \
+				 NFC_PROTO_ISO14443_B_MASK | \
+				 NFC_PROTO_ISO15693_MASK)
+
+struct virtual_nci_dev {
+	struct nci_dev *ndev;
+	struct mutex mtx;
+	struct sk_buff *send_buff;
+	struct wait_queue_head wq;
+	bool running;
+};
+
+static int virtual_nci_open(struct nci_dev *ndev)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	vdev->running = true;
+	return 0;
+}
+
+static int virtual_nci_close(struct nci_dev *ndev)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	mutex_lock(&vdev->mtx);
+	kfree_skb(vdev->send_buff);
+	vdev->send_buff = NULL;
+	vdev->running = false;
+	mutex_unlock(&vdev->mtx);
+
+	return 0;
+}
+
+static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	mutex_lock(&vdev->mtx);
+	if (vdev->send_buff || !vdev->running) {
+		mutex_unlock(&vdev->mtx);
+		kfree_skb(skb);
+		return -1;
+	}
+	vdev->send_buff = skb_copy(skb, GFP_KERNEL);
+	if (!vdev->send_buff) {
+		mutex_unlock(&vdev->mtx);
+		kfree_skb(skb);
+		return -1;
+	}
+	mutex_unlock(&vdev->mtx);
+	wake_up_interruptible(&vdev->wq);
+	consume_skb(skb);
+
+	return 0;
+}
+
+static const struct nci_ops virtual_nci_ops = {
+	.open = virtual_nci_open,
+	.close = virtual_nci_close,
+	.send = virtual_nci_send
+};
+
+static ssize_t virtual_ncidev_read(struct file *file, char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	size_t actual_len;
+
+	mutex_lock(&vdev->mtx);
+	while (!vdev->send_buff) {
+		mutex_unlock(&vdev->mtx);
+		if (wait_event_interruptible(vdev->wq, vdev->send_buff))
+			return -EFAULT;
+		mutex_lock(&vdev->mtx);
+	}
+
+	actual_len = min_t(size_t, count, vdev->send_buff->len);
+
+	if (copy_to_user(buf, vdev->send_buff->data, actual_len)) {
+		mutex_unlock(&vdev->mtx);
+		return -EFAULT;
+	}
+
+	skb_pull(vdev->send_buff, actual_len);
+	if (vdev->send_buff->len == 0) {
+		consume_skb(vdev->send_buff);
+		vdev->send_buff = NULL;
+	}
+	mutex_unlock(&vdev->mtx);
+
+	return actual_len;
+}
+
+static ssize_t virtual_ncidev_write(struct file *file,
+				    const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	struct sk_buff *skb;
+
+	skb = alloc_skb(count, GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	if (copy_from_user(skb_put(skb, count), buf, count)) {
+		kfree_skb(skb);
+		return -EFAULT;
+	}
+
+	nci_recv_frame(vdev->ndev, skb);
+	return count;
+}
+
+static int virtual_ncidev_open(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+	struct virtual_nci_dev *vdev;
+
+	vdev = kzalloc_obj(*vdev);
+	if (!vdev)
+		return -ENOMEM;
+	vdev->ndev = nci_allocate_device(&virtual_nci_ops,
+		VIRTUAL_NFC_PROTOCOLS, 0, 0);
+	if (!vdev->ndev) {
+		kfree(vdev);
+		return -ENOMEM;
+	}
+
+	mutex_init(&vdev->mtx);
+	init_waitqueue_head(&vdev->wq);
+	file->private_data = vdev;
+	nci_set_drvdata(vdev->ndev, vdev);
+
+	ret = nci_register_device(vdev->ndev);
+	if (ret < 0) {
+		nci_free_device(vdev->ndev);
+		mutex_destroy(&vdev->mtx);
+		kfree(vdev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int virtual_ncidev_close(struct inode *inode, struct file *file)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+
+	nci_unregister_device(vdev->ndev);
+	nci_free_device(vdev->ndev);
+	mutex_destroy(&vdev->mtx);
+	kfree(vdev);
+
+	return 0;
+}
+
+static long virtual_ncidev_ioctl(struct file *file, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	const struct nfc_dev *nfc_dev = vdev->ndev->nfc_dev;
+	void __user *p = (void __user *)arg;
+
+	if (cmd != IOCTL_GET_NCIDEV_IDX)
+		return -ENOTTY;
+
+	if (copy_to_user(p, &nfc_dev->idx, sizeof(nfc_dev->idx)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static const struct file_operations virtual_ncidev_fops = {
+	.owner = THIS_MODULE,
+	.read = virtual_ncidev_read,
+	.write = virtual_ncidev_write,
+	.open = virtual_ncidev_open,
+	.release = virtual_ncidev_close,
+	.unlocked_ioctl = virtual_ncidev_ioctl
+};
+
+static struct miscdevice miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "virtual_nci",
+	.fops = &virtual_ncidev_fops,
+	.mode = 0600,
+};
+
+module_misc_device(miscdev);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtual NCI device simulation driver");
+MODULE_AUTHOR("Bongsu Jeon <bongsu.jeon@samsung.com>");